Spinning solution



Patented July 20, 1937 UNIT SPINNING SOLUTIGN Camille Dreyfus, New York, N. Y., and William Whitehead, Cumberland, Md, assignors to Celanese Corporation of America, New York, N. Y., a corporation of Delaware No Drawing. Application February 4, 1928, Serial No. 252,030

2 Claims.

This invention relates to the preparation of yarns or films containing cellulose acetate from solutions containing the same.

An object of our invention is to prepare yarn 5 from a cellulose acetate, which yarn does not deluster when exposed to boiling water or other delustering agencies, that are apt to cause delustering of previously known cellulose acetate yarns.

A further object of our invention is to prepare yarn from acetone soluble cellulose acetate, which yarn will not become delustered or will become but little delustered when exposed to boiling water, wet steam or other delustering 15; agencies.

A further object of our invention is to vary the constitution of the solvent mixture used in the solution of cellulose acetate employed in spinning the yarn. Other objects of our invention will appear from the following detailed description.

Yarns'or fabrics produced from acetone soluble cellulose acetate or other cellulose acetates, when prepared in accordance with prior processes, lose their luster and become opaque when treated with hot or boiling water. This delustering action is accentuated by the presence of soaps or certain salts. Therefore in the Washing of such yarns or fabrics care must be taken that the temperature of the washing bath be not too high, else 6 delustering may result.

As an example of the prior methods of preparing yarns from acetone soluble cellulose acetate, it may be pointed out that such a cellulose acetate having an acetyl value for instance of 5 54.5% was dissolved in a solvent containing 95% of acetone and 5% of water. The solution thus formed is spun through the orifices of a spin neret, either into an atmosphere of elevated temperature, whereupon the solvent is evaporated, as

in the case of dry spinning, or into a precipitating bath as in the case of wet spinning. Yarns produced in accordance with this method display the often undesirable property of becoming delustered or crinkled when exposed to water or -5 wet steam at elevated temperature. Apparently the delustering of the yarn may be due to the fact that it becomes crinkled, and the surface thereof becomes pitted.

We have discovered the surprising fact that if 50 a cellulose acetate, as set forth above, is spun from a solution containing a larger percentage of a diluent for the solvent or a smaller percentage of a diluent than has heretofore been used, the tendency of the yarn to deluster decreases 55 With progressive increase of the proportion of diluent used, in the case where the larger percentages of diluents are used, until a point is reached where the tendency to deluster becomes practically nil; while this tendency to deluster decreases with progressive decrease of propor- 6 tions of diluent used in the case where the smaller percentages of diluents are used.

In accordance with our invention, yarns or films are made from a cellulose acetate, which forms yarns or films that tend to deluster as set 10 forth above, when spun in the old manner. This cellulose acetate is dissolved in a solvent containing either an appreciable proportion of diluent or very little if any diluent, and then is spun.

The cellulose acetate used in our invention may or may not be soluble in acetone, but We prefer to use an acetone soluble cellulose acetate having an acetyl Value of 52.5% to 56% and preferably 54.5% but this invention is not limited to the use of such cellulose acetate.

While we do not limit ourselves to a specific solvent to be used in our process, we have found that the use of acetone as the solvent gives excellent results. The diluent used may be water or any other suitable diluent. However, this invention will be more specifically described with respect to the use of water as the diluent.

The ratio of the acetone to water used in the solution may be varied within wide limits. Thus we have found that in those cases where a larger proportion of diluent is used, the solvent mixture may contain from 72% to 88% of acetone and from 28% to 12% of water respectively. Tests performed by using solvent mixtures of (1) 88% acetone and 12% water, (2), 84% of acetone and 16% of water, (3) 78% of acetone and 22% of water, (4) 76% of acetone and 24% of water, and (5) 72% of acetone and 28% of water, show that the tendency of the yarn to resist delustering when boiled, increases with the increase of the 46 percentage of Water used in the solvent until the ratio of 78% acetone to 22% of water is reached, at which point a maximum resistance to delustering and minimum tendency to become opaque when boiled in water is reached. In those cases where the proportion of water to acetone used is smaller than has been used heretofore, We have found that the percentage of water used may range from zero to about 2.5%, that is, the acetone used may be chemically pure containing 50 only approximately 0.06% water up to about 97.5% acetone, in which case we have observed that the less water present in the solvent mixture, the greater the resistance to delustering. In this connection it is pointed out that the viscosity of properties of the water.

the spinning solution bears a relation to the yarns produced thereby. Thus the viscosity of a solution of cellulose acetate in pure acetone is extremely high, while the viscosity of the solution decreases with the increase of the proportion of water until a point is reached corresponding roughly to 90% acetone and of water, after which the viscosity increases with further increase of the percentage of water present. 7

As stated before, the solution may be spun by a wet or by a dry spinning method. However, we prefer to employ a dry spinning method. In dry spinning, the temperature of spinning should be varied to take care of the difference of volatility of the solvent mixture; i. e. the greater the percentage of water used, the higher the temperature. Thus for chemically pure acetone, a spinning temperature of 50 to 55 C. may be used; for a solvent mixture containing 88% acetone and 12% water, a spinning temperature of 64 C. may be used; for a solvent mixture containing 84% acetone and 16% of water, a spinning temperature of 65 C. may be used; while for a solution containing 78% acetone and 22% water, a spinning temperature of 70 C. or more may be used. As illustrative of the importance of spinning temperatures under certain conditions, it may be pointed out that in spinning from a solvent mixture containing 76% of acetone and 24% of water, yarn produced while using a spinning temperature of 70 C. suffers little in luster and clearness when boiled in water for one hour, while yarn produced while using a spinning temperature of 60 C. becomes delustered and opaque more easily when boiled in water for minutes, in some instances.

Yarns produced by the above described method, when boiled in water or water containing soap or other alkaline material, or when exposed to wet steam, show a greatly increased resistance to delustering, as compared with yarns produced from a solution containing say 95% acetone and Moreover yarns prepared from solutions of cellulose acetate containing a large proportion of diluent (say 80% acetone and water) are more pliable than yarns prepared by the old method and may be knitted more closely.

In order to further illustrate our invention, but without intending to be limited thereto, the following detailed description of an example is given.

Example We take a cellulose acetate having an acetyl value of 54.5% and having a viscosity of 20 (as determined on an Ostwald viscosimeter with a solution containing 6 grams of the cellulose acetate and 160 grams of acetone, the viscosity of glycerine being called 100). This cellulose acetate is dissolved in a mixture containing 78% of acetone and 22% of water to form a solution containing approximately 25% of cellulose acetate. The solution is then filtered, and spun in a dry spinning machine, in which the solvent is evaporated oil at a temperature of 70 to 74 C., and

the thread thus formed is gathered up and wound or reeled. The yarn produced in this manner shows a remarkable resistance to delustering.

Thus while a yarn prepared from a solution containing 95% of acetone and 5% water becomes almost completely delustered or crinkled and opaque, when boiled in water for a period of 15 minutes, the yarn made in accordance with this example is not delustered at all or only slightly so, and its opacity is but slightly affected after boiling for 60 minutes. Even boiling in a 0.5% soap solution hardly affects the luster or opacity of the yarn prepared in accordance with this example.

The process of this invention may be applied to the obtaining of many beautiful effects in woven and knitted fabrics. For instance, a fabric may be woven of which the warp consists of yarn spun from a charge dissolved in a solvent mixture containing 78% of acetone and 22% of water while the weft may consist of a yarn spun from a charge dissolved in a solvent mixture containing 95% of acetone and 5% of water. The fabric may, for instance, be so woven that the warp oi the fabric will comprise say of one face of the fabric and the weft comprise say 7 of the other face of the fabric. This fabric may then be boiled either by separate treatment or in scouring, dyeing or finishing, with the result that the warp, which is highly resistant to delustering is hardly affected in appearance, while the weft becomes pronouncedly delustered and opaque, thus producing a fabric which is lustrous on one side and which has a dull matte appearance on the other.

By way of further illustration it is pointed out that lustrous figures or designs against dull background or vice versa may be obtained by weaving the two kinds of yarn by well known mechanical expedients of weaving, and by subsequently boiling or steaming.

While this invention has been described specifically with respect to the use of cellulose acetate, it may also be applied to such cellulose esters, such as cellulose formate, cellulose acetate, or cellulose propionate, that display the same properties as the cellulose acetate described above.

It is to be understood that the expression solvents of certain concentrations as used in the appended claims includes solvents or solvent mixtures of certain concentration or degree of admixture.

It is to be understood that the foregoing details are given merely by way of illustration and that many variations may be made therein without departing from the spirit of this invention.

Having described our invention what we claim and desire to secure by Letters Patent is:

l. A spinning solution for the production of artificial materials comprising cellulose acetate having an acetyl value of at least 52.5% and less than 56% dissolved in a solvent mixture containing from 88% to 72% of acetone and from 12% to 28% of water.

2. A spinning solution for the production of artificial materials comprising cellulose acetate having an acetyl value of at least 52.5% and less than 56% dissolved in a solvent mixture containing substantially 78% of ace-tone and substantially 22% of water.

CAMILLE DREYFUS. WILLIAM WHITEHEAD. 

